1. Field of the Invention
The present invention pertains to the field of control and manipulation of a digital audio signal by a user manipulable touch sensitive control surface. The present invention is specifically applicable to user manipulation of digital audio signals by disc jockeys (DJs).
2. Description of the Prior Art
Scratch effects controllers for live disc jockey musical performances (DJing) have become a popular replacement by DJs for conventional turntable and phonographic LP records for producing a “scratch effect” or to generally manipulate the speed and direction of music.
The original “scratch effect” is a very specific sound produced when a DJ simultaneously performs two actions. The DJ rotationally manipulates a vinyl record on a phonographic turntable in a rapid forward and backward movement. While doing this, the DJ also modulates the sound from the turntable on a DJ audio mixer, by quickly moving the mixer's cross fader back and forth in a rhythmic fashion.
Scratch effects controllers 100 have been developed to simulate this user manipulation of a vinyl record on a phonographic turntable. Instead of a turntable, phonographic record, needle, and magnet cartridge, the scratch effect controller generally contains a user rotatable mechanical disc 101. This user rotatable disc can come in a variety of forms including a vinyl, metal, or plastic disc, or a jog wheel. The surface is capable of freely rotating either clockwise or counter clockwise. There is generally some type of optical encoder and optical sensor operationally attached to the user rotatable disc to detect speed, relative position, and direction of rotation. Some controllers try to more accurately simulate the functionality of a conventional phonographic turntable by having a rotatable platter under the user rotatable disc 102. For example, see U.S. Pat. No. 6,541,690 to Segers and U.S. Pat. No. 7,072,249 to Huang. This platter is often driven by a motor in order to simulate the motion and feel of phonographic turntable platter. These arrangements tend to be bulky, heavy, expensive, and complex and therefore are not ideal for portable applications. In addition, the user rotatable disc is limited to rotary motion on the entire surface and can only be used for one function at a time. For example, the disc can be used to control a scratch effect, or jog and shuttle quickly through music passage, but not both at the same time.
DJ CD players 200 have incorporated similar functionality as the scratch effect controller. They typically have a rotatable jog wheel 201 that responds to circumferential motion by the user. As with the scratch effect controller, the user rotatable jog wheel is limited to rotary motion on the entire surface and can only be used for one function at a time. Because there is a mechanical rotating jog wheel or platter, DJ CD players 200 with a user rotatable surface tend to have complex mechanical arrangements and tend to be bulky, heavy, expensive, and not ideal for portable applications.
There have been attempts to solve the problem of portability. There are several DJ controllers that contain small lightweight mechanical or opto/mechanical rotary controls. These tend to be less accurate and more difficult to control, then the previously described controllers. They also suffer from the same limitation of allowing only one function at a time on the user manipulable disc.
Other attempts to solve the portability problem have included the use of a mouse with a personal computer and specialized software that creates a scratch effect from the mouse's motion. Creating a scratch effect with a mouse is not desirable because the act of grasping the mouse is cumbersome and hinders the DJ's performance. Alternately, a computer touch pad can be used in place of the mouse. The touch pad offers the advantage of potentially better control than the mouse but suffers several disadvantages: (1) only linear motion is possible, and (2) a standard touch pad can not provide direct visual feedback as to help the DJ refine their performance.
Rotary touch pads have been incorporated into portable audio devices 300. The typically have function switches 301 as well as a touch sensitive surface 302. The touch sensitive surface 302 responds to circumferential motion from the user. Because they tend to be small, performing an accurate scratch effect suitable for live performance by a professional DJ is not desirable. For this reason, devices have been created that externalize the critical performance control functionality. For example, see US 2007/0280489 to Roman.
Display technology has been incorporated into DJ platters. US 20070234889 to Rotolo de Moraes suggests the use of multiple sensor under the jog wheel control to provide discrete regions of functionality. In addition Rotolo de Moraes teaches visual feedback on a DJ control wheel through discrete LEDs mainly as a learning tool and to provide some type of scoring mechanism for competition. US 2007/0274181 to Yao teaches a way of providing visual feedback through the use of blinking lights on the platter surface.
However, none of the above mentioned devices solve the problem of portability, durability, and accuracy for creating scratch effects on a DJ control surface.